One of my disks in a raidz2 array crashed a few days ago and it was time to hotswap a disk. zpool status showed a faulted drive:

raidz2    DEGRADED     0     0     0
  c3t6d0  ONLINE       0     0     0
  c3t7d0  FAULTED     27 85.2K     0  too many errors
  c5t0d0  ONLINE       0     0     0
  c5t1d0  ONLINE       0     0     0

The disk is attached into an LSI Logic SAS1068E B3 SATA card which has eight SATA ports. I used lsiutil to find out that there were indeed some serious problems with the disk:

Adapter Phy 7:  Link Up
  Invalid DWord Count                                     306,006
  Running Disparity Error Count                           309,292
  Loss of DWord Synch Count                                     0
  Phy Reset Problem Count                                       0

I’m not sure what “Invalid DWord Count” and “Running Disparity Error Count” means, but that indeed doesn’t look good. I guess I need to do some googling after this. zpool status showed problems with disk c3t7d0 which is mapped into the 8th disk in the LSI card.

I replaced the old disk and added the new disk into the system on the fly. The LSI card noticed and initialized the disk, but with a different id. The disk is now c3t8d0. This is propably because the disk wasn’t the same. I ordered zfs to replace the old disk with the new one with command “zpool replace tank c3t7d0 c3t8d0”

raidz2       DEGRADED     0     0     0
  c3t6d0     ONLINE       0     0     0  14.2M resilvered
  replacing  DEGRADED     0     0     0
    c3t7d0   FAULTED     27 89.2K     0  too many errors
    c3t8d0   ONLINE       0     0     0  2.03G resilvered
  c5t0d0     ONLINE       0     0     0  14.2M resilvered
  c5t1d0     ONLINE       0     0     0  13.5M resilvered

That’s it. The resilver took me 3h16m to complete.